gistfile1.php

 public function createAction(Request $request, $package_id)
    {
        
        $package = $this->getPackage($package_id);
        $entity = new Prestation();
        $entity->setPackage($package);
        $form = $this->createCreateForm($entity);
        $form->handleRequest($request);

        if ($form->isValid()) {
            $em = $this->getDoctrine()->getManager();
            $em->persist($entity);
            $em->flush();

            return $this->redirect($this->generateUrl('prestation_show', array('id' => $entity->getId())).
                    '#prestation-' . $entity->getId()
                    );
        }

        return $this->render('TestTestBundle:Prestation:new.html.twig', array(
            'entity' => $entity,
            'form'   => $form->createView(),
        ));
    }


    private function createCreateForm(Prestation $entity)
    {
        $form = $this->createForm(new PrestationType(), $entity, array(
            'action' => $this->generateUrl('prestation_create'),
            'method' => 'POST',
        ));

        $form->add('submit', 'submit', array('label' => 'Create'));

        return $form;
    }


 public function newAction($package_id)
    {
        $package = $this->getPackage($package_id);
        $entity = new Prestation();
        $entity->setPackage($package);
        $form   = $this->createCreateForm($entity);

        return $this->render('TestTestBundle:Prestation:new.html.twig', array(
            'entity' => $entity,
            'form'   => $form->createView(),
            
        ));
    }
 protected function getPackage($package_id)
    {
        $em = $this->getDoctrine()->getManager();

        $package = $em->getRepository('TestTestBundle:Package')->find($package_id);

        if (!$package) {
            throw $this->createNotFoundException('Unable to find Blog post.');
        }

        return $package;
    }